If there is a bright side to the never-ending war on rust, it's the fact that because the risk of rust is so prevalent, a lot of products on the market will help you prevent rust from forming or get rid of it should it crop up in some unprotected corner of your rig. We could fill a whole catalog with rust prevention and removal products, but because we don't have that kind of space, here's a short list of goods to help you keep body rot at bay.
Rust Converter
If you want to chemically alter a rotted area before painting, Eastwood offers a two-part Rust Converter that turns the rusted metal into an inert black oxide that can then be painted over, or covered with the company's Rust Encapsulator.
OxiSolv
A phosphoric-acid-based rust remover, OxiSolv dissolves rust and leaves a zinc-phosphate coating on the metal to help prevent the formation of flash rust (which can occur before the bare metal is painted, since the remover is neutralized with water). Like most acid-based solutions, OxiSolv works faster at warmer temperatures; in fact, you can heat it up to 100 degrees F for fastest results. This chemical is more aggressive than the non-acid-based dissolvers, and it will etch the metal if left on too long. (Note: Naval Jelly, which is sold by several different chemical companies, is another phosphoric-acid-based rust dissolver.)
POR-15
One of the best-known antirust products, POR-15 is a rust-preventative, polyurethane sealer that can be applied directly to rusted or "seasoned" (as the company calls it) metal, once you've cleaned the loose rust off of it. POR-15 dries to a hard, nonporous finish that prevents rust from reoccurring by acting as a barrier between the metal and further exposure to moisture. POR-15 is available in pints, quarts, and gallons; or you can buy it in a number of kits designed to treat specific areas, such as floor pans, fuel tanks, and steering wheels.
Rust Encapsulator
It's tempting to consider this Eastwood's version of POR-15, especially since, like POR-15, Rust Encapsulator can be brushed directly onto rusted metal and will prevent the rust from spreading. The two have different chemical compositions, however (the Encapsulator is a slow-cure fortified enamel), and the Encapsulator includes fine glass flakes that help it form an oxidation barrier. Available in aerosol cans as well as pints, quarts, and gallons.
Rust Dissolver
Rust removal chemistry falls into two broad categories: acid based and acid free. Eastwood's Rust Dissolver is an acid-free solution that, through the process of chelating, bonds to the rust and pulls it away from the metal. It's gentle enough not to affect materials around it, from other metals like copper, brass, and aluminum to plastic, rubber, wood, and vinyl. The Dissolver works best when the part is submerged in the solution, though Eastwood says you can MacGyver-up a system using an aquarium pump to keep the rusted part wet during chelating.